At present, Ethernet ring is widespread and applied gradually. FIG. 1 is a schematic illustrating the structure of a single Ethernet ring. With reference to FIG. 1, a single Ethernet ring includes a master node and multiple transmission nodes, and the master node and transmission nodes are adapted to transmit service data on the Ethernet ring and fulfill various service functions.
As to a single Ethernet ring, Rapid Ring Protection Protocol (RRPP) can provide an effective protection mechanism at present. RRPP is a link layer protocol specially applied in an Ethernet ring. When the Ethernet ring is integrated, RRPP can prevent broadcast storm caused by a data ring; when a link on the Ethernet ring is broken, RRPP can rapidly start a backup link so as to guarantee the maximum connectivity of the Ethernet ring.
As shown in FIG. 1, according to RRPP protocol, when a single Ethernet ring is running normally, the master node only opens the primary port on one side for data messages, and blocks the secondary port on other side. In this way, the Ethernet ring is in a chain form in stead of forming a loop when transmitting the data messages.
According to RRPP protocol, in a single Ethernet ring, fault detection and fault processing include: a master node periodically sends a Hello message from its primary port; the master node determines that the Ethernet ring where it is located is down if the master node does not receive the Hello message sent by itself in a predefined period of time, or if the master node receives a fault notification message reported by a transmission node, or if the master node detects that a link directly connected to one of its ports is at fault; and the master node transfers to a down state, opens the blocked secondary port, and sends out a forward-table updating message. According to RRPP protocol, fault recovery detection and fault recovery processing include: a master node periodically sends a Hello message; after the Ethernet ring is down, if the master node can receive the Hello message it has sent, or if the master node receives a fault recovery message reported by a transmission node, or if the master node detects that a link directly connected to one of its ports is up, the master node determines that the Ethernet ring where it is located has recovered, opens the blocked secondary port and sends out a forward-table updating message.
In a single Ethernet ring, when the node of the Ethernet ring directly connected to the fault link detects that the fault has been eliminated, the node will firstly set the fault recovery port into a blocked state, and start a blocking timer. When the node receives a forward-table updating message sent by the master node or when the blocking timer is out, the node will transfer the port from the blocked state to a state of normally forwarding messages, so as to guarantee smoothness of the link.
With the development of services, a single Ethernet ring sometimes cannot meet the requirement of the services. In practical network application, it is usually needed to intersect multiple Ethernet rings arbitrarily to form an intersecting ring network. In other words, an intersecting ring network may include multiple Ethernet rings, each of the Ethernet rings corresponds to an Ethernet topology in form of ring connection, and the intersecting ring network is constituted by the multiple Ethernet rings intersected with one another. FIG. 2 is a schematic illustrating a topology structure formed by multiple intersected Ethernet rings. With reference to FIG. 2, Ethernet ring R1 (composed of S1, S2, S3 and S4), R2 (composed of S3, S2 and S6) and R3 (composed of S3, S2 and S5) are intersected to form an intersecting ring network with arbitrary topology.
The networking manner of intersecting multiple Ethernet rings can form a more flexible network topology structure, so as to provide richer services for users. Due to characteristics of Ethernet ring itself, as to the intersected Ethernet rings, an effective ring network protection mechanism is also needed to guarantee smoothness of links in the ring network and to avoid forming a loop. As shown in FIG. 2, it is not only needed to prevent Ethernet rings R1, R2 and R3 from forming a loop, but also needed to guarantee a big ring generated via intersection (like the ring formed by S1, S2, S6, S3, S4 and S1) from forming a loop. Further, it is needed to consider what kind of measures should be adopted when an Ethernet ring like R1 is down, so as to guarantee smoothness of the other Ethernet rings, and so forth.
However, at present, there is only effective Ethernet ring protection mechanism for a single Ethernet ring, but there is no effective ring network protection mechanism for an arbitrary topology formed by intersected multiple Ethernet rings.